Fuses have been used for many years to provide over current and short circuit protection for electrical circuits. Frequently, fuses are grouped and mounted in fuseblock assemblies such that when one fuse blows, it must be identified from among the group before it can be replaced.
There are many devices in the prior art which have been developed to aid in the detection of a blown fuse by providing a visual or audible indication upon failure of a fuse. Examples of these of which the inventor herein is aware include Linton U.S. Pat. No. 2,492,302 which discloses a fuse indicator which clips on to the fuse barrel and extends from one end terminal to the other and which lights up to indicate a blown fuse; Poehlman U.S. Pat. No. 3,457,535 is a similar device which has pigtail conductors to provide adjustability; Glueckert U.S. Pat. No. 3,071,760 discloses a plug in fuse with a built in alarm circuit that provides an audible signal upon fuse rupture; Kauffman U.S. Pat. No. 2,074,921 discloses a device for attachment to barrel type fuses which provides a visual signal upon fuse failure and also a mechanical means to handle the fuse; German Pat. No. 28-31-139 discloses a fuse monitoring circuit which includes light emitting diodes (LED); and Dutch Pat. No. 7503-428 which also discloses a fuse indicating circuit incorporating LED's.
Although these prior art devices generally disclose the concept of providing an indication when a fuse blows, there is neither disclosed nor suggested a pocket-size, hand held testing device which has adjustable contact members for testing fuses of varying length and which can be inexpensively produced in injection molded plastic parts which require little assembly to produce a finished device. The inventor herein has succeeded in developing such a device with a translucent housing with LED's at one end, and one which has fixtures at the other end of the handle to facilitate removal of the blown fuse, and insertion of a replacement fuse. Thus, the invention includes a handle member with an integrally formed translucent housing at one end thereof and which receives a base plate having structure to receive and mount a PC board in contact with pivotally mounted contact members, the PC board having LED's mounted thereon to illuminate and indicate a blown fuse when the contact members are touched to the fuse clips or terminals at either end of the fuse. At the opposite end of the handle member is an integrally formed fixture for blade type fuses as disclosed in parent application Ser. No. 354,381 filed May 3, 1982, the disclosure of which is incorporated herein by reference, as well as a hook shaped member which is snapped into the handle member and which can pivot about the handle member for removing barrel type fuses. All of the pieces comprising the device are plastic injection molded, except for the PC board and its circuit, the drive pin which mounts the PC board, and the pivotal contact members.
One of the unique features of the invention includes the ability to pivotally mount each contact member to the base plate and PC board so that the contact members may be adjusted for different size fuses without losing electrical contact with the PC board and circuit. Each contact member has a post which extends through a hole in the PC board, the PC board being pressure fit against the contact member posts by a knurled drive pin which is inserted through another hole in the PC board and into the base plate. The contact members can thus maintain their electrical contact with the circuit of the PC board as they pivot with respect to each other and with respect to the tool. This permits the contact members to be freely moved to bridge across various sized fuses and test them. On the bottom of the base plate is a pentagon shaped stop which contacts a nib on each contact member to limit movement of the contact members and prevent their coming in contact with each other.
This new invention provides many advantages over the fuse indicators of the prior art through its inexpensive construction, ease of assembly, unique feature of pivoting contact members and the means of maintaining them in electrical contact with the PC board indicator circuit, the stop means to prevent electrical shorting of the contact members, the knurled drive pin which provides contact pressure between the PC board and the contact members, the pair of fixtures at the other end of the handle for removal and insertion of fuses, and all of these features being packaged in a pocket sized tool.
A brief description has been given to facilitate an understanding of the invention. The invention may be more fully understood by studying the drawings and the description of the preferred embodiment which follows.